See javascript source code if you wanna use this. Prepare to write some JS!
<script>
	fridge = function() {
		return {
			space: 5,
			
			// Items is from left to right, where the door hinge is on the left and
			// the door is fully opened. Therefore the first item is the leftmost
			// item, but the first grabbable item (before the door is sufficiently
			// opened) is the rightmost item.
			items: ["fresh milk",
					"sterilized milk",
					"chocolate milk",
					"syrup",
					"pudding"],
			
			timeTaken: 0, // measured in 'retrievals of the right-most index'
			// A value of 3.1 means that it took as much time as retrieving the last item 3.1 times
			
			get: function(item) { //item is a zero-based integer, or "first" or "last"
				if (item == -1)
					throw new Error("Item -1!");
				
				switch (item) {
					case "first":
						return this.get(0);
					
					case "last":
						return this.get(this.items.length - 1);
					
					default:
						this.timeTaken += 1 + ((this.items.length - item - 1) / this.items.length);
						this.items.splice(item, 1);
						return this;
				}
			},
			
			store: function (item, position) { //string, zero-based int or "first" or "last"
				if (position == -1)
					throw new Error("Position -1!");
				
				if (this.items.length > this.space) {
					throw new Error("Fridge door is already full!");
					return this;
				}
				
				// Check how much time the storage took
				if (position == "last")
					this.timeTaken += 2;
				else if (position == "first")
					this.timeTaken += 4;
				else
					this.timeTaken += 6 + ((this.items.length - position - 1) / this.items.length);
				
				if (position == "first")
					position = 0;
				
				if (position == "last")
					position = this.items.length - 1;
				
				this.items.splice(position, 0, item);
				return this;
			}
		};
	};
	
	var myfridge = new fridge();
	
	var entities = {
		person1: {
			usage: {
				"fresh milk": 1,
				"sterilized milk": 0.5,
				"chocolate milk": 1.2,
				"syrup": 0.7,
				"pudding": 0.4
			},
			personWeight: 1
		},
		person2: {
			usage: {
				"fresh milk": 1,
				"sterilized milk": 0,
				"chocolate milk": 0,
				"syrup": 0,
				"pudding": 0
			},
			personWeight: 0.6
		},
		person3: {
			usage: {
				"fresh milk": 0.7,
				"sterilized milk": 0.9,
				"chocolate milk": 0.55,
				"syrup": 0.65,
				"pudding": 0.7
			},
			personWeight: 2
		}
	};
	
	totalPersonWeight = 0;
	for (var i in entities) {
		var totalWeight = 0;
		for (var j in entities[i].usage) {
			totalWeight += entities[i].usage[j];
		}
		entities[i].totalWeight = totalWeight;
		totalPersonWeight += entities[i].personWeight;
	}
	
	function run(mode, onlyFirst, undef) {
		if (onlyFirst == undef)
			onlyFirst = true;
		
		var ops = 1000 * 100;
		
		switch (mode) {
			case "pushLast":
				for (var i = 0; i < ops; i++) {
					var first = true;
					for (var j in entities) {
						if (myrand(totalPersonWeight) < entities[j].personWeight) {
							for (var k in entities[j].usage) {
								if (myrand(entities[j].totalWeight) < entities[j].usage[k]) {
									var originalPosition = search(myfridge, k);
									myfridge.get(originalPosition);
									
									if (!onlyFirst || first) {
										myfridge.store(k, "last");
									}
									else {
										myfridge.store(k, originalPosition);
									}
								}
							}
						}
						first = false;
					}
				}
				break;
			
			case "justPutItBack":
				for (var i = 0; i < ops; i++) {
					var first = true;
					for (var j in entities) {
						if (myrand(totalPersonWeight) < entities[j].personWeight) {
							for (var k in entities[j].usage) {
								if (myrand(entities[j].totalWeight) < entities[j].usage[k]) {
									var originalPosition = search(myfridge, k);
									myfridge.get(originalPosition);
									myfridge.store(k, originalPosition);
								}
							}
						}
						first = false;
					}
				}
				break;
		}
		console.log(myfridge.timeTaken / ops);
		myfridge.timeTaken = 0;
	}
	
	function search(fridge, item) {
		for (var i in fridge.items)
			if (fridge.items[i] == item)
				return i;
		
		return -1;
	}
	
	function myrand(multiply) {
		return Math.random() * multiply;
	}
</script>